Ribavirin improves treatment response to peginterferon in chronic hepatitis C but the mechanism remains controversial. We studied correlates of response and mechanism of action of ribavirin in treatment of hepatitis C. 70 treatment-nave patients were randomized to 4 weeks of ribavirin (1000-1200 mg/d) or none, followed by peginterferon alfa-2a and ribavirin at standard doses and durations. Patients were randomized to undergo a liver biopsy either 24 hours before, or 6 hours after starting peginterferon. Hepatic gene expression was assessed by microarray and interferon-stimulated gene (ISG) expression quantified by the nCounter platform. Temporal changes in ISG expression were assessed by qPCR in peripheral-blood mononuclear cells (PBMC) and by serum levels of IP-10. After four weeks of ribavirin monotherapy, HCV levels decreased by 0.5 log10 (p=0.009 vs. controls) and ALT by 33% (p<0.001). Biochemical, but not virological response to ribavirin monotherapy predicted subsequent response to combination treatment (rapid virological response, 71% in biochemical responders vs. 22% non-responders, p=0.01; early virological response, 100% vs. 68%, p=0.03, sustained virological response 83% vs. 41%, p=0.053). Ribavirin pretreatment, while modestly augmented the induction of ISGs by peginterferon, did not modify the virological response of subsequent treatment with peginterferon and ribavirin. Ribavirin monotherapy caused a decrease in serum IP-10 levels but had no effect on ISG expression in PBMC. Ribavirin is a weak antiviral but its clinical effect in combination with peginterferon seems to be mediated by a separate, indirect mechanism, which may act to reset the interferon responsiveness in HCV-infected liver. Ribavirin pretreatment does not alter the clinical outcome of subsequent combination therapy. Human embryonic stem cells (hESCs), human induced pluripotent stem cells (hiPSCs) and the technology to developmentally program these cells to various cell lineages offer great promise for cell therapy of various diseases. Recently, different protocols to differentiate them into hepatocytes-like cells (HLC) have been described. In this context, we hypothesize that this approach could be useful in developing a relevant model for HCV infection in vitro. Moreover, the hiPSCs approach could allow the generation of patient-specific hepatocytes with promising opportunity for cell therapy of viral liver diseases. We have generated hiPSCs from primary fibroblasts using lentiviruses or Sendai virus vectors, and characterized them in comparison to hESCs. Human pluripotent stem cells were efficiently differentiated into HLC, as demonstrated by induction of the expression of hepatic markers and the secretion of hepatic proteins (AFP and albumin) in the supernatants. Moreover these cells recapitulate hepatocyte-specific metabolic functions like lipid and glycogen accumulation, and indocyanin green metabolism. These HLC can be infected with HCV. The infected cells also respond to antiviral therapy, such as interferon-a and 2'-methylcytidine, a nucleoside analog inhibitor of HCV polymerase. HCV infection also induces intrinsic innate immune response including interferon response. To show whether it is possible to successfully engraft these cells and establish functional human hepatocytes in vivo, we engrafted, via intra-splenic injection, 2-4 millions DHHs into the liver parenchyma of immune-deficient transgenic mice carrying the urokinase-type plasminogen activator gene driven by the major urinary protein promoter (MUP-uPA/SCID/Bg). Human albumin (hALB) could be detected in the serum of the engrafted mice by ELISA as early as day 10 post-engraftment, with concentrations ranging from 0.4 to 2.3 mg/mL. More importantly, hALB persisted for more than 4 months, consistent with long-term engraftment of human cells in the mouse liver parenchyma. Mice were sacrificed 4 months post-engraftment, and liver sections were assessed by immunostaining for a variety of human proteins (albumin, alpha-1-antitrypsine, alpha-fetoprotein). Areas of human cells were observed around central veins, and could constituted up to 15% of the mouse liver parenchyma. 2 weeks post-engraftment, mice with high hALB concentration were inoculated with HCV positive sera of different genotypes (1a, 1b, 3). Serum samples were obtained at day 30, 60 and 90 post inoculation, and assessed for HCV RNA by RTqPCR. HCV RNA could be detected in the serum of every mouse at day 60 post-inoculation. HCV increased up to 90 days post-infection, consistent with long-term infection of engrafted human hepatocytes in the mouse liver. Conclusion. We demonstrate here that hESCs- and hiPSCs-derived DHHs can be efficiently engrafted into the mouse liver parenchyma, and that they can be infected by HCV(+) sera of different genotypes. This approach constitutes a valuable model to study HCV infection in the context of patients genetic background as well as in the native architecture of the liver. In conclusion, we demonstrated that HLC derived from human pluripotent stem cells support infection by HCV in vitro and in vivo. Moreover, generation of iPSC from primary fibroblasts would allow us to generate patient-specific HLC, and thus reproduce in vitro a personalized model for the HCV infection. Moreover, by targeting proviral cellular factors or introducing antiviral factors in these cells, we can generate HCV resistant-patient specific-hepatocytes. This approach holds great promises for cell therapy of hepatitis C, particularly for patients with end-stage liver diseases.